This invention relates to a brake for a portable stand and, in particular, to a brake which is rugged and self-locking yet can be easily set and released.
Stands, carts, and the like have long been provided with wheels to enable them to be moved without being lifted. Brakes have been provided, typically adjacent at least two wheels, for holding a stand in place. There are many types of brakes, all of which lower a foot to the floor and slightly lift the stand or at least bear a substantial fraction of the weight of the stand. Of the many types of brakes, this invention relates to brakes which use a combination of toggle joint and plunger, such as described in U.S. Pat. No. 2,712,366--Skupas--and in U.S. Pat. No. 3,735,841--Auriemma. In the Skupas patent, a pair of bell crank levers and links straddle a telescoping leg and are attached to each end of the leg. In the Auriemma patent, a compound lever extends a square tube held on three sides by a bracket attached to a cart.
For tool stands in particular, commercially available brakes are not strong enough to bear the weight of the tool, permitting the stand to rock or move when the tool is used. In a brake such as disclosed in the Auriemma patent, the tube is not held sufficiently securely to prevent motion when a force is applied at a large (relative to the height of the brake) distance from the floor. Heavy tools such as jointers and table saws make the problem more severe because their center of gravity is high.
Another problem is setting and releasing the brake. Brakes typically include an over-center mechanism in which the weight of the stand, and whatever is on the stand, bears down on the brake, locking the brake in an extended position. A toggle joint is typically designed for ease in setting the brake but not for ease in releasing the brake. While this assures that the brake is securely set, the brake is often difficult and inconvenient to release. The Auriemma patent discloses using an auxiliary lever for releasing the brake to solve this problem. While effective, the brake mechanism described in the Auriemma patent is complicated and expensive. The brake described in the Skupas patent relies on separate foot pedals for setting and releasing the brake and the pedals are inconveniently located close to the underside of the cart.
For tool stands which are frequently moved, by contractors for example, the brake mechanism must be rugged and easily operated. It is highly desirable that the brakes on one side of a stand be ganged and actuated simultaneously by a common bar or handle. In addition, the brakes should be actuated wherever a force is applied along the handle, i.e. it should not be necessary to apply a force at the center of the handle to actuate the brakes simultaneously.
The number of power tools and tool stands sold each year is considerable. Typically the tool stands do not include wheels or brakes. Presently available aftermarket kits are not rugged enough to withstand use or to hold the tool in place without rocking. There is thus a need for a brake kit for adding wheels and brakes to tool stands.
In view of the foregoing, it is therefore an object of the invention to provide a brake suitable for use on stands for heavy tools.
Another object of the invention is to provide a self-locking brake that is easily set and released.
A further object of the invention is to provide a brake that does not permit wobble or other motion of the brake when the brake is set.
Another object of the invention is to provide a brake kit which can be attached easily to existing portable stands.
A further object of the invention is to provide a brake which can be ganged with like brakes and actuated simultaneously.